1 48 ANIMAL LIFE PAST AND PRESENT. 



unfortunately the case that there are still many gaps 

 in the chain which should link all the existing Giant 

 Birds together, but we may confidently hope that the 

 progress of geological research will little by little reduce 

 the number and length of these gaps. 



All the Giant Birds, it may be observed, both living 

 and extinct, are linked together by their incapacity of 

 night, and the consequent absence of that strong bony 

 ridge or keel which we may observe on the breast- 

 bone of a duck or a fowl, and the presence of which is 

 essential to form a firm support for the powerful 

 muscles required to move the wings. Whether, however, 

 this incapacity for fiight is a feature which was always 

 possessed by the Giant Birds, or whether it has been 

 gradually acquired by disuse, is a question which has 

 exercised the minds of those best fitted to decide it ; 

 but the probability is that it is an acquired one. 

 Moreover, in saying that the Giant Birds are incapable 

 of flight, it must by no means be inferred that all 

 birds in that condition have any affinity to this group. 

 On the contrary, the opposite is the case, since in the 

 extinct Dodo of the Mauritius we have an instance of 

 a huge pigeon which had evidently lost the power of 

 night ; and the superficial deposits of New Zealand have 

 yielded the remains of a large rail and a goose which 

 were also in the same predicament. These and other 

 flightless birds differ, however, essentially in several 

 parts of their organisation from the true Giant Birds, 

 and thus have no sort of connection with the subject 

 of this chapter. There are, however, certain birds, 



